1. Field of the Invention
This invention relates to a tubular connector for transfer of fluids or circulation of fluids in industrial or automotive applications.
2. Description of the Prior Art
As is well known in the field of making tubing, tubing is essentially easiest to make in straight elongated form, such as by extrusion. Such straight tubing, when made in large rolls can then be cut to various sizes for use in a variety of applications. One such application might be in automobiles, or trucks, etc., for the connection of the engine to the radiator so that the hot fluid produced within the engine can be transferred to a radiator where the fluid is then cooled and circulated back into the engine where the cooled fluid is again heated by the combustion heat produced by the engine. Thus, a variety of automobiles, or trucks, etc., in which the engine is spaced a different distance from the radiator, or in which the inlet and outlet pipes from the engine and radiator are offset in a variety of directions and positions, may be able to use the same type of tubing from the same original tubing supply roll, by simply cutting the tubing to different lengths and elastically bending the tubing as needed to accommodate the various arrangements of engines and radiators.
These connector tubes are primarily fastened to the inlet and outlet pipes by some sort of clamping device which fits over an end of the connector tube, and which presses the connector tube into tight engagement with the pipe. Such a clamping device is usually provided in addition to the connector, and is slid into place over the connector before the connector is applied to the pipe. Applying a clamping device in such a manner, however, can pose several disadvantages, firstly, the clamp would need to be held into place during preliminary tightening, thus requiring the user to use both hands to fasten the connector into place, and secondly, the position of the clamp on the connector may not always be in the most desirable location along the connector, which could thus lead to leakage if not correctly positioned.
There is also essentially one problem which arises in making straight tubing and then adapting it to a variety of uses, especially if the use requires that the tubing be sharply bent. In so bending the tubing, a phenomenon called kinking often occurs, which phenomenon is well known to both the producers and the users of the tubing. Kinking describes the ovalisation and subsequent local pinching of the tubing as the tubing is bent, so that if the tubing is bent to have a small radius of curvature, complete blockage of the interior passage of the tubing is possible. This pinching usually occurs when a tube is bent beyond an acceptable limit. Such pinching can also be described as a folding of the tube wall which is located to the inside of the bent tubing.
In the remainder of the present description, kinking will be used to designate the phenomenon described above.
The prior art includes three types of solutions to the problem of kinking.
The first solution comprises the fabrication of bent tubes, in which various processes are used to give the tubes the shape they must have for their intended application. Curved tubes, or elbows, of this type are described in Japanese Patent 61,206,633, which has Yokahama Rubber as patentee, where the result is achieved by casting with a process using lead, according to an old technique which is well known in the rubber transformation industry; in International Patent WO 8302989, which has Norskhydro as patentee, in which the shaping is performed on a press; in U.S. Pat. No. 4,242,296, which has Dayco as patentee; or Japanese patents 57,120,427, which has Tokai Rubber as patentee, or 61,206,632, which has Yokahama Rubber as patentee, in which the shape is imparted by vulcanization on a mandrel having the desired geometry; or 59,169,835, which has Kurashiki Kako as patentee, where the tube is cast in a mold after having been covered with inorganic powder; or 53,079,977, which has Bridgestone Tire as patentee, where the shape is obtained by molding with an inflatable mandrel; or 61,041,522, which has Tiger Polymer as patentee, where the curved tube is realized by blow-moulding.
These techniques for the fabrication of bent tubes make it possible to produce tubes with the geometry desired for the application, but whose shapes and sizes are rather strictly limited, and do not offer any protection against kinking if, as the result of improper workmanship, or by accident, the tube is bent along a radius which is smaller than intended. Moreover, the realization techniques are frequently complex and require the use of heavy equipment, such as presses, blow-moulding installations, lead presses and material to strip off the lead coating.
The second solution to the problems of kinking comprises the realization of straight tubes which will accept small radii of curvature. The methods most often used include:
The reinforcement of the wall by use of a rubber-based mixture with a high modulus of elasticity, with the possible incorporation of short fibers, such as the realizations described in U.S. Pat. No. 4,522,235 and European Patent 32352 (Goodyear tire and Rubber), or European Patent Application 74747 (Parker Hannifin); PA1 an excellent adherence between the constituent elements of the wall of the tube--which may or may not include reinforcement elements--as described in Japanese Patents 61,153,088 (Nitta Mua), 59,147,184 (Toyo Rubber) and 55,097,948 (Meij Rubber), in Dutch Patents 7,506,969 (Polymer) and 6,709,089 (Angus), or in U.S. Pat. No. 8,383,258 (Alfred Roberts & Son); PA1 the reinforcement of the wall by one or more textile and/or metal reinforcement elements, which are described in a large number of publications, such as German Patents 3,508,444 (Holterus) or 2,751,323 (Bindl), U.S. Pat. Nos. 4,553,568 (Goodyear Tire and Rubber) or 4,460,140 (Nordson), French Patents 2,541,420 (Caoutchouc Manufacture et Plastiques) or 2,475,683 (Bodinier), British Patents 2,076,926 (Bridgestone Tire) or 1,379,544 (Moss), European Patent 121,691 (Grohe) and Austrian Patent 6,449,822 (George Angus); PA1 an additional reinforcement by the addition of ribs or grooves, as described in U.S. Pat. No. 4,258,755 (Bandag), Canadian Patent 1,012,905 (Dayco), or Belgian Patent 715,296 (Tubigomma); PA1 an element which allows irreversible curvature after fabrication, such as a deformable ring, as proposed by the European Patent 34491 (Gates Rubber); PA1 maintenance of the circular cross section by the addition of rigid rings, as described in German Patent 3,312,926 (Aerocontact), U.S. Pat. No. 4,157,101 (Goodyear Tire and Rubber), or 3,858,615 (Puritan Bennett), or the use of U-shaped elements, as described in Belgian Patent 896,329 (Dillon).
The third method used to prevent kinking is the addition of mechanical means integrated into the tube, or external mechanical means which prevent curvature beyond acceptable limits. Such means are described in French Patent 1,462,731 (BTR Industries) and Russian Patent 573,666 (Fomin).
Whatever the method considered, the solutions proposed have the disadvantage that they increase the weight of the tube (as a result of the reinforcements, i.e., the rings), reduce the flexibility (by increasing the bonding between constituents or by incorporating reinforcement elements) and complicate the fabrication process. A simpler solution is proposed in German Patent 2,929,923 (Metronic Electronic), which solution uses a polyurethane foam tube for an air bubble massage installation.
The proposed polyurethane tube, however, would not be suitable for the transport of fluids, on account of cavitation phenomena which occur when fluids come in contact with the structure containing the polyurethane cells.
Moreover, the material selected, polyurethane, is sensitive to hydrolysis and attack by various chemical media, and could not be used for the transport of steam or corrosive products. Finally, to constitute a tube by itself, it would require the installation of an internal or external coating, which would allow it to withstand the internal pressure strains and abrasion, common in fluid handling operations.